title: Association between vaginal birth after cesarean delivery and primary cesarean delivery rates.
abstract: OBJECTIVE
  To estimate the association between vaginal birth after cesarean delivery (VBAC) rates and primary cesarean delivery rates in California hospitals.
  
  
  METHODS
  Hospital VBAC rates were calculated using birth certificate and discharge data from 2009, and hospitals were categorized by quartile of VBAC rate. Multivariable logistic regression analysis was performed to estimate the odds of cesarean delivery among low-risk nulliparous women with singleton pregnancies at term in vertex presentation (nulliparous term singleton vertex) by hospital VBAC quartile while controlling for many patient-level and hospital-level confounders.
  
  
  RESULTS
  There were 468,789 term singleton births in California in 2009 at 255 hospitals, 125,471 of which were low-risk nulliparous term singleton vertex. Vaginal birth after cesarean delivery rates varied between hospitals, with a range of 0-44.6%. Rates of cesarean delivery among low-risk nulliparous term singleton vertex women declined significantly with increasing VBAC rate. When adjusted for maternal and hospital characteristics, low-risk nulliparous term singleton vertex women who gave birth in hospitals in the highest VBAC quartile had an odds ratio of 0.55 (95% confidence interval 0.46-0.66) of cesarean delivery compared with women at hospitals with the lowest VBAC rates. Each percentage point increase in a hospital's VBAC rate was associated with a 0.65% decrease in the low-risk nulliparous term singleton vertex cesarean delivery rate.
  
  
  CONCLUSIONS
  Hospitals with higher rates of VBAC have lower rates of primary cesarean delivery among low-risk nulliparous women with singleton pregnancies at term in vertex presentation.
  
  
  METHODS
  II.
authors.affiliation: Departments of Obstetrics, Gynecology, and Reproductive Sciences, Epidemiology & Biostatistics, and Medicine, University of California, San Francisco, San Francisco, California; and the Department of Obstetrics and Gynecology, Oregon Health & Science University, Portland, Oregon.
authors.forename: Melissa G
authors.initials: MG
authors.lastname: Rosenstein
authors.forename: Miriam
authors.initials: M
authors.lastname: Kuppermann
authors.forename: Steven E
authors.initials: SE
authors.lastname: Gregorich
authors.forename: Erika K
authors.initials: EK
authors.lastname: Cottrell
authors.forename: Aaron B
authors.initials: AB
authors.lastname: Caughey
authors.forename: Yvonne W
authors.initials: YW
authors.lastname: Cheng
mesh_terms: D000328:Adult; D001719:Birth Certificates; D002140:California; D002585:Cesarean Section / Q000706:statistics & numerical data*; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D005260:Female; D006761:Hospitals / Q000706:statistics & numerical data; D006801:Humans; D016017:Odds Ratio; D010298:Parity; D011247:Pregnancy; D012307:Risk Factors; D016064:Vaginal Birth after Cesarean / Q000706:statistics & numerical data*